1. Field of the Invention
The invention relates to semiconductor processing, and more particularly to methods of determining particle contamination in semiconductor processing tools.
2. Description of the Related Art
The manufacturing of semiconductor devices requires high levels of cleanliness during the numerous manufacturing processes. For example, the surface of semiconductor wafers must be thoroughly cleaned of particle contaminants prior to processing. Further, films, such as dielectric films or metal films deposited on the semiconductor wafer, must also be thoroughly cleaned of particle contaminants. If not removed, contaminants on wafers and films may affect device performance characteristics and cause device failures to occur at faster rates than expected otherwise. Therefore, many of the processing steps are conducted in xe2x80x9cclean roomsxe2x80x9d to reduce possible particle contamination.
Nevertheless, semiconductor devices can become contaminated, and rendered defective, by contaminants during the various process steps. For example, during the various processing steps, contaminants can be introduced from the numerous processing tools because of incomplete cleansing of reagents from the tools.
Conventionally, determining the source of particle contamination in semiconductor processing tools involves primarily detective work. One must systematically look throughout the tools for the most probable source of the particle contamination source(s) until the source is identified. For example, once it is determined that particle contamination is a problem in a processing tool, the tool must be taken off-line until the contamination source can be identified and cleaned. Thus, the presence of particle contaminants in semiconductor processing tools can lead to time consuming searches for the source of the contamination.
Reducing particle contamination from semiconductor processing tools quickly is therefore of high importance. Tool downtime can be very costly as semiconductor processing is slowed or halted while the contamination source is located and cleaned. Further, accurately determining the source and eliminating the particle contamination is vital for producing high-quality semiconductor devices. Therefore, quickly and accurately determining the source of particle contamination in a semiconductor processing tool and returning the tool to service is of great importance.
A need exists, therefore, for a method to quickly diagnose whether contaminant particles are located in a film (dielectric or metal) deposited on a wafer, or rather on the surface of the film. This information allows one to quickly localize and determine specific areas of the semiconductor processing tool that may be the source of the particle contamination.
The present invention provides a method for qualitatively determining the location of contaminant particles on a semiconductor wafer with a film deposited thereon, and to localize areas of the processing tool as likely sources of the contamination.
According to one embodiment of the present invention, a method for determining the location of contaminants on a semiconductor wafer comprises obtaining a first particle count of the wafer, scrubbing the wafer, obtaining a second particle count of the wafer after scrubbing the wafer, and determining the location of the particles based on the first and second particle counts.
The method may further comprise removing only the particles on the surface of the wafer with a scrub. The scrub may be a non-contact brushless scrub, such as a D-sonic water scrubbing tool. The wafer further comprises a dielectric film or a metal film deposited thereon. The scrub removes only those particles on the surface of the film, and leaves behind those particles within or below the film. One can determine qualitatively that the particles are within a film formed thereon if the second particle count is substantially the same as the first particle count, and determine that the particles are on the surface of the wafer if the second particle count is less than the first particle count.
According to another embodiment of the present invention, a method for determining the source of particle contaminants in a semiconductor processing tool comprises the steps of obtaining a first particle count of a wafer with at least one film deposited thereon, scrubbing the wafer, obtaining a second particle count of the wafer after scrubbing the wafer, and localizing areas of the processing tool where the particle contamination originates from.
The method may further comprise comparing the first particle count with the second particle count, examining the film deposition portion of the processing tool if the first particle count and second particle count are substantially the same, and examining the portion of the processing tool that prepares the wafer for exit after the deposition if the first particle count is substantially less than the first particle count.